This application claims the priority of German Patent Applications, Serial Nos. 101 44 482.6, filed Sep. 10, 2001, and 102 20 166.8, filed May 6, 2002, pursuant to 35 U.S.C. 119(a)-(d), the subject matter of which is incorporated herein by reference.
The present invention relates to a computer-aided control method for a machine tool which can be used to machine a workpiece by cutting, for example, by turning in a lathe.
Control methods, wherein a control command is provided to a control computer, based on which the workpiece is machined with a tool over a contiguous region and over a total height, and wherein the control computer automatically determines a number of travel paths based on the control command, with the workpiece successively machined over a partial height until the total height is reached, are known in the art. These control methods simplify and automate machining by allowing larger contiguous regions of a workpiece to be cut.
Conventional methods determine the travel paths so that the partial height (sometimes also referred to as cutting depth) is constant. This can cause premature tool wear through the formation of grooves in the cutting tool. This premature wear can be prevented by avoiding the use of such control commands. In other words, wear can only be prevented if a machine operator manually programs each travel path. This approach is not only time consuming and arduous, but more importantly may cause errors.
It would therefore be desirable to modify the conventional computer-aided control methods for a machine tool so as to prevent or at least significantly reduce premature wear of the machining tool.
According to an aspect of the invention, a computer-aided control method for a machine tool adapted for machining a workpiece by cutting, in particular by lathe turning, includes providing a control command to a control computer, based on which the workpiece is machined with a tool over a contiguous region and over a total height, with the control computer based on the control command automatically determining a number of travel paths, based on which the workpiece is machined in the region over a partial height and altogether over the entire height, wherein the determined travel paths have variable partial heights.
In this way, the wear of the cutting tool is thereby evened out by distributing the wear over a larger area of the tool. This increases the service life of the tool.
The increased complexity of the travel paths is hereby transferred to the computer-aided determination of the travel paths. Advantageously, the travel paths have to be determined only once and can be tested in advance. This approach makes it possible to cut different partial heights even for arbitrary contours, so that the process is not limited to machining only cylindrical or flat parts, but parts of arbitrary geometry, for example cast parts.
Advantageous embodiments of the invention may include one or more of the following features.
The partial height can be constant during the travel paths, but can vary between the travel paths. Alternatively, the partial height can vary during at least one of the travel paths, or during each of the travel paths. The partial height can vary continuously or in steps, as well as alternatingly or monotonously.
The partial height can vary between a minimum value and a maximum value, with a maximum value between 2 and 10 mm, whereby the ratio of minimum value to maximum value can be between 0.5 and 0.9, in particular between 0.6 and 0.8, or more particularly between 0.65 and 0.75. The ratio of minimum value to maximum value can also be preset in the control computer as a parameter.
If the partial height is only varied when the control computer issues a release command, then varying the partial height can be blocked if such a variation is not desired in certain situations.
Further aspects of the invention include a computer program product for carrying out the aforedescribed control method as well as a control computer executing the computer program product.